Hire the best Electrician

diagnosing an intermittently tripping RCB, how to diagnose?

Results 1 to 14 of 14
  1. #1
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default diagnosing an intermittently tripping RCB, how to diagnose?

    i have a RCB randomly tripping and have no idea what is going on. its in a hotel room.
    the breaker controls about 5 power points along a wall, it will trip maybe 2-3 times a week and cannot work out why.
    it has a small bar fridge, tv and microwave on them. i have even swapped out these appliances to another room to see if it will trigger another room but no it doesnt.
    i have unplugged these things and it still randomly trips.
    could it be a faulty RCB??
    what is my next step of checking before getting electrician in?? if any?

  2. #2
    Seasoned DIY droog's Avatar
    Join Date
    Sep 2005
    Location
    Bendigo
    Age
    58
    Posts
    2,879

    Default

    Could be a faulty RCD, but could also be something wrong with the circuit.
    Are the 5 GPO’s the only things on the circuit ?, and certain nothing else.

    Even build up of dirt behind a GPO or in a junction box with a bit of moisture can be enough.

  3. #3
    Community Moderator
    Join Date
    Dec 2008
    Location
    Queensland
    Posts
    7,746

    Default

    You can get proper RCD testers that will test the tripping current and time to trip. My neighbour got one from work and we tested my place and found one circuit was tripping at 15MA not 30 MA I tracked it down to a faulty surge arrester that was leaking to ground.

  4. #4
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default

    yeah i found my rcd tester tonight i will use tomorrow on it. nothing else on the circuits that i know of. its been pretty dry up here as well, very little to no rain. i'm wondering if it maybe also could be rats or something in the roof chewing cables.

  5. #5
    2K Club Member
    Join Date
    Apr 2012
    Location
    Jarrahdale
    Posts
    2,070

    Default

    I had this thrice of late.
    The leccy came around and we started disconnecting the Loop In- Loop out GPOs until the RCD stayed on. This then let us know which "end" of the circuit to look at. If the RCD stays on, then the fault is AFTER that GPO. If not then it's before. Then you go to the next one and disconnect and see if the RCD stays on. This lets you narrow down where the fault may be. The first time for me it was a faulty outdoor GPO. Swapped and all good. The second time we thought it was the same as we replaced the GPO with a new Clipsal Series 2000 and it stayed on. Closer examination of the rear of the old GPO showed a slug across the active and neutral...
    The last time was indeed rats had chewed the insulation off all three conductors. If not for the RCD we may have lost the house, in the worst case.
    And.....your point is.....what exactly?

  6. #6
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default

    problem with mine is its that intermittent it would takes months to diagnose that way. went off last night as well, empty room.
    i checked the rcd with a tester i have and they trigger right on 30ma and not below. next step i guess. see if anything on back of any of them.

  7. #7
    Community Moderator
    Join Date
    Dec 2008
    Location
    Queensland
    Posts
    7,746

    Default

    Intermittent faults take a bit to find, rats chewing cable, white ants back GPO.

  8. #8
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default

    that is why im doing as much as i can before calling electrician.

  9. #9
    Community Moderator
    Join Date
    Dec 2008
    Location
    Queensland
    Posts
    7,746

    Default

    The electrician would have a megger and while 1 Meg is a pass mark in fact it should be a lot more than that which would give you a clue.

  10. #10
    1K Club Member
    Join Date
    Dec 2012
    Location
    Country NSW
    Posts
    1,501

    Default

    An insulation test of the whole circuit will be the best way to find it if it's not a faulty RCD. Checking the back of every GPO is a good idea, I have even found black ants in the back of GPOs tripping an RCD.
    A loose neutral connector on the consumer mains can even trip RCDs, so sometimes these can be a bit tricky to find. And just lately I've found a couple of mice that have zapped themselves on the back contact screws of the GPOs, these were both intermittent tripping similar to yours despite the mouse not moving because it had been dead for a while.
    Swapping the RCD over with another one would be the quickest and easiest way to check the RCD.
    Never argue with idiots, they will drag you down to their level and beat you with experience.


  11. #11
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default

    i will see what happens today after i unplugged everything on that breaker. will leave it that way for a few days see if trips.

  12. #12
    Seasoned DIY droog's Avatar
    Join Date
    Sep 2005
    Location
    Bendigo
    Age
    58
    Posts
    2,879

    Default

    Quote Originally Posted by wozzzzza View Post
    i will see what happens today after i unplugged everything on that breaker. will leave it that way for a few days see if trips.
    Unplugging all devices will not confirm the problem is not in the circuit, as it is an imbalance in the active neutral currents that trips the RCD. A high impedance connection between neutral and ground such as dirt or ant nest will only trip the RCD if there is current draw on that circuit.

  13. #13
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default

    ok i will pull power points off tomorrow have a look behind them.

  14. #14
    2K Club Member
    Join Date
    Mar 2008
    Location
    Cairns
    Posts
    2,360

    Default

    but if it is an appliance that is triggering it, i have moved them to another room and that other room will have a tripped RCB from now on.

Similar Threads

  1. Diagnosing Mould on upper walls and ceilings.
    By bfsoriginal in forum Roofing
    Replies: 4
    Last Post: 2nd Sep 2021, 04:23 PM
  2. Replies: 15
    Last Post: 17th Mar 2021, 12:07 PM
  3. how do diagnose a faulty hot plate regulator??
    By wozzzzza in forum Electrical
    Replies: 16
    Last Post: 24th Oct 2017, 08:32 PM
  4. Replies: 52
    Last Post: 24th May 2016, 03:28 PM
  5. Diagnosing a humming and not starting Pool Pump
    By DaleBlack in forum Pools, Spa & Water Features
    Replies: 9
    Last Post: 29th Nov 2015, 12:13 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •